Verizon today released its earnings results from the December quarter and reported a loss of $2.02 billion, or $0.71 a share. During the same quarter a year-ago, the US-based carrier reported a loss of $2.64 billion.

Apple wise, Verizon sold an impressive 4.3 million iPhone devices. All told, smartphone sales for the quarter came in at 7.7 million units, meaning that Apple’s iPhone accounts for over 55% of every smartphone Verizon sold during the quarter.

As for the compay’s quarterly loss, two issues are at play.

One, Verizon had a one-time adjustment to the value of its pension plan last quarter which affected operating income. And two, keep in mind that Verizon, like every other carrier, pays large subsidies to Apple for the iPhone. Consequently, Verizon makes a profit on each iPhone sold months after the point of sale.

Usually, Verizon’s overall revenue increase is driven higher monthly wireless service revenues, as it gains customers. But this quarter, the largest contributor to the rise in revenue was phone sales, which doubled from last year to $2.2 billion.

Verizon Wireless added 1.2 million new subscribers on contract-based plans, which are the most lucrative. It was the second-best result in the last two years, further solidifying the company’s position as the industry leader, with 87.4 million phones and other devices on contract-based plans, and 108.7 million total.

Later today, Apple will release its own earnings with some analysts expecting Apple’s December quarter iPhone sales volume to come in in the 32 million range.